a Last.FM Strategy for OmniAuth

lastfm.rb

require 'omniauth/core'
require 'digest/md5'
require 'rest-client'
require 'multi_json'

module OmniAuth
  module Strategies
    class LastFM
      include OmniAuth::Strategy

      attr_accessor :api_key, :secret_key, :options
      def initialize(app, api_key, secret_key, options = {})
        super(app, :lastfm)
        @api_key = api_key
        @secret_key = secret_key
        @options = options
      end

      def request_phase
        params = {:api_key => api_key }
        query_string = params.map{ |key,value| "#{key}=#{Rack::Utils.escape(value)}" }.join('&')
        redirect "http://www.last.fm/api/auth/?#{query_string}"
      end

      def callback_phase
        token = request.params['token']
        params = { :api_key => api_key }
        params[:token] = token
        params[:api_sig] = signature(token)
        params[:method] = "auth.getSession"
        params[:format] = "json"
        response = RestClient.get('http://ws.audioscrobbler.com/2.0/', { :params => params })
        @json = MultiJson.decode(response.to_s)
        super
      end

      def auth_hash
        OmniAuth::Utils.deep_merge(super, {:lastfm => @json['session']})
      end

      protected
      def signature(token)
        sign = "api_key#{api_key}methodauth.getSessiontoken#{token}#{secret_key}"
        Digest::MD5.hexdigest(sign)
      end
    end
  end
end

hi Brandon,

I'm still tweaking some stuff on it and it's lacking some tests. For instance, naming it LastFM name doesn't work if you're using Devise, it should be Lastfm (or your setttings should point to :last_f_m, which is damn ugly)